Performance of the MGIT TBc Identification Test and Meta-Analysis of MPT64 Assays for Identification of the Mycobacterium tuberculosis Complex in Liquid Culture

Abstract

Rapid MPT64-based immunochromatographic tests (MPT64 ICTs) have been developed to detect Mycobacterium tuberculosis complex (MTBC) in culture. We demonstrated the noninferiority of one commercial MTP64 ICT, the MGIT TBc identification (TBcID) test, to GenoType line probe assays for MTBC identification in positive MGIT cultures. Meta-analysis of MPT64 ICT performance for identification of MTBC in liquid culture confirmed similar very high sensitivities and specificities for all three commercial MPT64 assays for which sufficient data were available.Early tuberculosis case detection underpinned by qualityassured bacteriology is a cornerstone of the WHO Stop TB strategy (32). WHO has endorsed wider implementation of liquid mycobacterial culture in high-burden countries to improve diagnostic sensitivity and culture turnaround times (29-31). However, rapid and accurate identification of Mycobacterium tuberculosis in positive cultures is essential for translating these benefits into earlier diagnosis and treatment for patients-particularly as liquid culture is associated with isolation of more nontuberculous mycobacteria (NTM) (2, 31). Conventional biochemical identification methods are slow, requiring subculture onto solid media, and cost and limited laboratory capacity preclude nucleic acid amplification tests (NAAT) in low-resource settings. Rapid immunochromatographic tests (ICT) that detect the M. tuberculosis complex (MTBC) MPT64 protein are cheaper and simpler to use and thus may have an important role in these and other settings. We compared one MPT64 ICT, the MGIT TBc identification test (TBc ID; Becton Dickinson, Sparks, MD), with the GenoType MTBC and Mycobacterium CM/AS line probe assays (LPA; Hain Lifescience Gmbh, Nehren, Germany) and present a meta-analysis of MPT64 assay performance for MTBC identification in liquid culture.Between August 2009 and June 2011, clinical samples from two Kenyan hospitals were processed using the MGIT 960 system (BD Diagnostics, Sparks, MD) and standard protocols (3, 27). Ziehl-Neelsen (ZN)-stained smears from positive cultures were examined for acid-fast bacilli (AFB), and an aliquot was inoculated onto blood agar to detect contamination (defined as growth after 48 h of incubation at 37°C). Further aliquots from AFB-positive cultures were used to perform TBcID and LPA according to manufacturers' instructions. When results were discordant, we repeated both tests, performed the Xpert MTB/RIF assay (Cepheid, Sunnyvale, CA) using the original specimen and culture broth, and reviewed the clinical notes. Assuming an LPA sensitivity of 99% (8) and a smallest acceptable true difference (delta) of 5%, a sample size of 83 MTBC isolates was required to demonstrate the noninferiority of TBcID to the LPA with 90% power.TBcID and LPA results were concordant for 208 (83 MTBC and 125 non-MTBC isolates; 99%) of 210 AFB-positive cultures (kappa ϭ 0.98; 95% confidence interval [CI], 0.84 to 1.0),

Extra pulmonary tuberculosis: Rapid identification of Mycobacterium tuberculosis grown in Mycobacterium growth indicator tube 960 and Lowenstein-Jensen media, employing Standard diagnostics Bioline Mycobacterium tuberculosis protein 64 antigen detection kit

“…Several reports from different countries recorded specifi city of nearly 100% and sensitivity ranging from 95% to 100% for the rapid MPT64 antigen detection kits in comparison to conventional methods for identifying MTB. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] We have experienced 100% sensitivity and specifi city of this particular kit in comparison to conventional techniques. Our local strains are thus recognised by SD Bioline kit of Korean origin.…”

Commercial MPT64-based tests for rapid identification of Mycobacterium tuberculosis complex: A meta-analysis

“…MPT-64 based tests for identification of MTC addition to rapidity, commercial MPT64-based ICTs are less expensive and technologically simper than molecular methods and biochemical method. 5 Therefore, commercial MPT64-based ICTs are better choices for MTC identification in resource-limited countries.…”

“…So far, 3 commercial MPT64-based ICT kits have been introduced for rapid identification of MTC, including Capilia TB assay (TAUNS, Numazu, Japan), SD Bioline Ag MPT64 rapid assay (Standard Diagnostics, Yongin, South Korean) and BD MGIT TBc ID test (Becton Dickinson, Sparks, USA). 5 The principles of these commercial kits are identical and described as follows.…”

Pulmonary Disease Caused by Non-Tuberculous Mycobacteria

“…Once growth is detected, M. tuberculosis should immediately be excluded by use of antigen-based rapid tests [e.g. the Capilia TB assay (TAUNS, Izunokuni, Japan) or the MGIT TBc ID Test (Becton, Dickinson and Company], PCR, or line probe assays [89]. If NTM are identified, they should be taxonomically differentiated to the level of complex, species, or subspecies depending on their clinical relevance.…”